1. Industrial useful field
This invention relates to an improvement in a damper disc which can increase or decrease a hysteresis torque generated in accordance with a change of torsion angle.
2. Prior art
Utility Model No. 55-12598 has conventionally been known as this type of clutch disc. In this conventional embodiment, two friction washers 12 are provided so as to hold a flange 10a of a spline hub 10 between them, friction plates 14 are pressed by a cone spring 15 on external sides of the friction washers 12 respectively, and projections 14a are formed on inner peripheral parts of the friction plates 14, as shown in FIG. 7. These projections 14a are made fit in two side plates 14 in such a manner that they can slide freely each other within a specified torsion angle, a small hysteresis torque is generated by the friction plates 14 within a small torsion angle at which the side plates 16 and the friction plates 14 are slidable each other, and a large torsion torque is generated by the friction plates 14 and the friction washers 12 when the torsion torque becomes large.
In the above-mentioned conventional embodiment, however, a large force would be applied on the projection 14a to lessen a strength of the projection 14a because the projection 14a is provided at the inner peripheral part. Further, since it is necessary to form a notch 16a for passing through the projection 14a on the side plate 16, a deviated wear on a contact surface between the friction plate 14 and the side plate 16 is apt to occur and a specified hysteresis torque can not be obtained if the above deviated wear occurs.
Further, in case of the construction as illustrated in FIG. 7, the small torsion angle can generate only a minimum hysteresis torque so that obtainable characteristics are confined. Therefore, in case when a comparatively large hysteresis torque of about 50% of the large torsion angle, for example, is required even in the small torsion angle range, the required hysteresis characteristics can not be obtained.